Sling



Oct. 18, 1966 c, w. WHAPLES ETAL 3,279,841

United States Patent 3,279,841 SLING Charles W. Whaples, Cambridge, Md., R. E. Lee Mowbray, deceased, late of Cambridge, Md., by Clara H. Mowbray, executrix, Cambridge, Md, assignors to Cambridge Wire Cloth Company, Cambridge, Md., a corporation of Maryland Filed Oct. 8, 1964, Ser. No. 402,648

24 Claims. (Cl. 29474) This invention relates to a metallic sling and more particularly to a metallic sling formed of a longitudinally extendible belt member and relatively inextendible side plate members.

Heretofore, metallic slings have been fabricated solely of a woven wire fabric. Certain properties of this sling are very desirable. It is longitudinally elastic, longitudinally flexible, laterally stable, and it provides a relatively large bearing area for the load being lifted.

However, this type of sling has several disadvantages. For instance, the sling is susceptible to failure along an edge. Once the edge is ruptured, the sling is progressively ripped across its width. The initial edge rupture often occurs as a result of off-center loading. Thus, in lowering extended lengths of pipe line into ditches the slings are invariably loaded on the edge towards which the pipe is sloping downwardly. Inasmuch as the load is carried by one edge of the sling, rather than being dispersed across the width of the sling, this edge is occasionally ruptured with the eventual failure of the entire sling.

The sling has the disadvantages of susceptibility to overstretching to a point of rupture or any other predetermined point and susceptibility to being crushed by heavy loads.

Broadly, therefore, the purpose of this invention is to overcome the disadvantages heretofore mentioned while retaining the advantages of this type of sling.

One of the purposes of this invention, therefore, is to strengthen the unsupported longitudinally extending edges of the sling. If a stronger material were merely incorporated into the sling as an outer edge, the outer edges only would support the object being carried with the central portion of the sling serving as a mere filler. The outer edges would have to break before any tension would be put on the central portion. Thus, it is a further object of this invention to retain the supporting capabilities of the entire width of the sling while strengthening the unsupported edges of the sling.

More specifically, it is an object of this invention to provide a metallic fabric sling comprising a pair of opposed support members; a flexible metallic belt member for carrying a normal load transversely secured to the support members and extending longitudinally therebetween with a plurality of rods transversely secured thereto; and means operatively associated with at least two of the rods and extending longitudinally between the support members along the longitudinal unsupported edge of the belt for additionally carrying the load once the belt member has been stretched a predetermined amount by a predetermined load, such as one which stretches the belt member to a degree approaching its yield point.

Still another object of this invention is to provide a sling having a woven wire fabric belt member of one tractive pitch and a plurality of plate members extending along the unsupported longitudinal edge portion of the belt of a greater tractive pitch so that under loads up to a predetermined tractive load, such as a load which stretches the belt to a degree approaching the yield point of the woven wire belt, the only load bearing member is the woven wire belt and at or above this predetermined tractive load, when the tractive pitch of the woven wire belt equals the tractive pitch of the plate members, the

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load is divided between the woven wire belt and the plate members. According to the preferable form of the invention, the woven wire belt member comprises a plurality of elongated helical spirals preferably of right-hand twist and of left-hand twist alternately disposed between the support members, although any type of helically spiraled woven wire belt member could be used. The spirals have the arcuate vertexes at the ends of the convolutions of each spiral intermeshed and hingedly interconnected by transverse rods extending alternately through the arcuate vertexes of the convolutions of adjacent spirals. The woven wire belt portion assumes its elasticity or extendibility from the fact that the spirals tend to elongate or flatten out further under tension or traction. The plate members are pivotally secured to the rods and are slotted in at least one end so as to be slidably positioned on the rods. The plate members do not bear any of the tractive load until the spirals have elongated to a point where the tractive pitch of the spirals equals the tractive pitch of the plate members. At this point both components of the sling will bear the tractive load irrespective of whether the load is centered or off-centered. Thus, when the load is centered, the woven wire belt portion and the plate members on both sides of the sling share the load. When the load is off-centered, both components still share the load, but it may be that only the plate member on the load side of the sling is stressed. It will be appreciated that inasmuch as the plate members are relatively inextendible, except for what little elasticity there is in the metal itself, these members will provide a means to prevent the spirals from overstretching, such as beyond a degree approaching their yield point.

A further object of this invention is to provide a metallic sling comprising a pair of opposed support members, a flexible metallic belt member having a plurality of rods secured thereto, and a supplemental load carrying means for additionally carrying the tractive load after the belt member has been stretched to a degree approaching its yield point. The supplemental load carrying means, however, is pivotally connected to the ends of two of the rods with the rods being spaced from one another by at least one rod which is free of direct connection to said supplemental load carrying means.

It is still a further object of this invention to provide a means for preventing the woven wire fabric from being crushed under the load. This object of the invention is accomplished by the provision of the plate members. Preferably the plate members have a height equal to or greater than the height of the spirals when they are stretched to a degree approaching their yield point so as to prevent the spirals from being crushed.

Moreover, it is a further object of this invention to provide an elastic coating means covering at least the surfaces of the woven wire fabric and of the supplemental load carrying means which bear against the load so as to prevent the load from being damaged.

For clarity, it might be pointed out that the load (i.e., pipe length, etc., being carried by the wire fabric or sling) subjects the fabric to two different types of forcesa tractive load substantially in the plane of the-fabric and a compressive load normal to the plane of the fabric. The type of load referred to in the specification will be readily apparent from the context in which the term is used. Generally, the load is a tractive load, for the invention, except for one modification, is designed to combat failure due to tractive loads.

These and other objects of this invention are more clearly depicted in the following detailed description having specific reference to the attached drawings in which the embodiments of the invention are shown, not to limit the scope of the invention in any respect but so that the principles thereof might be more clearly demonstrated.

In the drawings:

FIGURE 1 is a plan view of the sling with the elastic coating referred to above partially broken away to expose the metallic structure of the sling;

FIGURE 2 is a fragmentary perspective view showing the supplemental load carrying members and spirals in detail under no load or low load conditions;

FIGURE 3 is a fragmentary perspective view showing the supplemental load carrying members and spirals in detail under straight line loading at or above the pre determined tractive load for which the supplemental load carrying members are designed;

FIGURE 4 is a perspective view showing one of the supplemental load carrying members;

FIGURE 5 is a perspective view of one of the supplemental load carrying members having slotted openings at each end;

FIGURE 6 is a perspective view showing an embodiment of the sling being used in laying pipe;

FIGURE 7 is a fragmentary plan view of the sling subjected to off-center loading such that the tractive load on one edge is at or above the predetermined tractive load for which the supplemental load carrying members were designed and the tractive load on the other edge is less than this predetermined load; and

FIGURE 8 is a fragmentary perspective view of another embodiment of the sling.

A sling 10 is shown in FIGURE 1 comprising a belt member 12 for carrying the normal load of the sling transversely connected at its ends 14 to a pair of support members 16 and 18 and extending longitudinally therebetween. Each of the support members, 16 and 18, are preferably plate-like in configuration and each has a plurality of apertures 20 for receiving lift forks or the like after the sling has been placed under a load. It will be appreciated that the support members may assume other configurations such as are commonly used in the art. The belt member has a plurality of rods 22 transversely secured thereto.

As shown more particularly in FIGURE 2, the belt member 12 preferably comprises a woven wire fabric 24 made up of a plurality of transversely disposed elongated or flattened helical spirals 26 which are hingedly interconnected by a plurality of transverse rods 22. Each helical spiral or coil has a pair of rods extending therethrough so that each rod is oppositely disposed in the arcuate vertexes 28 at the ends 29 of the convolutions 30 of each spiral 26. Adjacent spirals are intermeshed to the extent that at least a second spiral is seated on each rod. A belt member utilizing such a spiral fabric preferably comprises spirals of right-hand or clockwise twist 32 and spirals of left-hand or counterclockwise twist 34 alternately disposed between the support members 16 and 18 and hingedly interconnected by transverse rods 22 extending alternately through the arcuate vertexes 28 at the ends 29 of the convolutions 30 of adjacent spirals 26. The alternate use of spirals of right-hand and left hand twists prevents the sling from twisting under load. While the embodiments of the invention disclosed herein show the use of alternating right-hand and left-hand twist, any type of spiral member can preferably be used with the principles disclosed herein. By the nature of the structural characteristics of spirals, these spirals, although somewhat already elongated, will tend to be further elongated or flattened under load thereby varying the longitudinal distance 36 between adjacent rods. Moreover, while the belt member is shown as a woven wire belt member preferably comprising a plurality of spiral members, it will be appreciated that the belt could be made of any metallic fabric which is longitudinally extendible.

As shown more particularly in FIGURE 7, the belt member is transversely secured to the support members 16 and 18, by any type of commonly used securing means 38. When the belt member comprises a plurality of spirals, it is preferably to secure the oppositely disposed outermost spirals 40 to the support members by connecting spirals 42. The convolutions 44 of these connecting spirals are preferably considerably more circular in transverse configuration than the elongated spirals which comprise the main body of the woven Wire belt member so that they may be easily threaded into suitable openings 46 in the support members 16 and 18. It will be appreciated, however, that it is within the scope of the invention to eliminate the outermost disposed rods and connect the outermost spirals 40 directly to the support members rather than operatively securing the spirals to the members by some intermediary means such as the coil spiral 42.

In addition to a flexible metallic belt member, the sling comprises means 48 positioned on the transverse rods 22 and extending along the longitudinal sides 50 of the belt for additionally carrying the load. This supplemental load carrying means 48 only carries the tractive load in response to the belt member being stretched a predetermined amount such as near the belt members yield point or elastic limit by a predetermined load. In order to provide a safety factor and to cover variances in the yield points of spirals, the supplemental load carrying means as an illustration, carries the load in response to the belt member being stretched to a degree approaching the yield point of the belt. Under loads up to a degree approaching the yield point of the belt, the only load bearing member is the belt. At or above this degree, the load is divided between the supplemental load carrying means and the belt as illustrated in FIGURE 3. By delaying the introduction of the load carrying capacity of the supplemental load carrying means until this point, the inherent characteristics of the two load carrying components of the sling can be utilized to the fullest. Obviously, other predetermined load values can be established for bringing the supplemental load carrying means into operation. Moreover, it will be appreciated that the predetermined loads will vary, depending on the size of the belt member and type of material used in the belt member. For instance, there are a variety of loads, depending on the size of the sling and the material used in the sling, which will stretch the belt member to a degree approaching its yield point.

While it is within the scope of the invention to use any mechanical structure suitable for accomplishing the objects heretofore set forth, the supplemental load carrying means in the preferred form of the invention comprises a plurality of members 52, such as plate-like links, each having opposed ends 54 and 56 as shown in FIGURE 4. Each end has a hole 58 extending therethrough by which the members are pivotally positioned on adjacent rods. At least one of the holes 60 is slotted so that the members are slidably, in addition to being pivotally, positioned on the rod. On the other hand, both of the holes may be slotted as illustrated in FIGURE 5.

The supplemental load carrying means has attractive pitch 62 greater than the tractive pitch 64 of the woven wire belt elements under no load conditions as shown in FIGURE 2. For the purpose of this invention, tractive pitch is defined as the distance or pitch between the rod-bearing surfaces 66 of a particlar element when the load, being carried by the sling and hence the rods, tends to draw the element apart. Thus, when the belt comprises a plurality of spirals, the initial tractive pitch of the spirals is the distance between the rod-bearing vertexes 28 of a particular spiral as the sling is initially subjected to load. As the load increases, the rods elongate the convolutions of each spiral, thus the tractive pitch increases. The tractive pitch of the members is that pitch when the load is great enough to elongate the convolutions sufliciently to allow the rods to rest in the outer disposed rod-bearing surfaces 66 of the hole and/or slot of a particular member as illustrated in FIGURE 3. At this point the load exerts a force on the member which tends to draw it apart. Due to the fact that in the preferable form of the invention the members are relatively inextendible, except for the little inherent elasticity in the metal itself, the members are not extended to any appreciable amount, and the spirals are prevented from stretching beyond a degree approaching their yield point or any other predetermined point.

In the preferable form of the invention the initial tractive pitch of the members is equal to the tractive pitch of the spirals when the spirals are subjected to a predetermined load, such as a load which will stretch the spirals to a degree approaching the yield point or elastic limit of the spirals. In other words, the tractive pitch of the members is longer than the tractive pitch of the spirals "by the amount of stretch of the spirals up to, for example, a degree approaching their yield point.

Therefore, when the tractive pitch of the spirals is less then the initial tractive pitch of the members, the load is below the particular predetermined load and the only load bearing element is the spirals. However, when the tractive pitch of the spirals equals the tractive pitch of the members, the load is divided between the spirals and the members.

As shown more particularly in FIGURE 7, the supplemental load carrying means 48 is secured by attaching means 68 to the support members and is held on the rods 22 by securing means 70 such as by nuts or by enlarging the heads of the rods. The supplemental load carrying means is interconnected, preferably by means of rods, so as to extend continuously between the opposed support members, 16 and 18, and along the opposed longitudinal sides or unsupported ends 50 of the belt member. It will be appreciated, however, that it is within the scope of this invention to have the load carrying means extend in a non-continuous manner it it is only desirable to interconnect a few r-ods. Such a construction might be necessary if the object to be carried has a sharp edge which might rupture the belt, and hence additional edge support is desired in a localized region. As illustrated in the drawings, when the members are continuous, there are at least two members positioned on each rod, except perhaps the opposed outermost rods, which alternately extend in opposite directions. The outermost rods 72 could have just one member in a continuous connection with the rod being connected to the support member by attaching means 68 other than a member. As illustrated, the attaching means comprises a truncated member 74 which is welded to the support member 16. Furthermore, the drawings show that there are a large number of members positioned on each rod. It will be appreciated, however, that the number of members to be positioned on adjacent rods can vary along the length of the sling with respect to the tractive force exerted between these adjacent rods.

Heretofore, the supplemental load carrying means has been described as being positioned on adjacent rods. In reality, however, the supplemental load carrying means needs only to be operatively associated with at least two of the rods. As illustrated in FIGURE 8, the members 52 are seated on every other rod with an intermediate rod 75 disposed between the two rods on which the member is positioned. It is within the scope of the invention to space the rods having the plate positioned thereon from one another by more than one intermediate rod which is left free to direct connection with the member 52.

The rods used in this application may be of any common type although the intermediate rods 75 are preferably crimped rods such as disclosed in the patent to Hooper, 2,885,164, of May 5, 1959.

It will be appreciated that when one or more intermediate rods 75 are disposed between the plate member receiving rods 77 and 7.9, the plate member will have a tractive pitch greater than the total net initial tractive pitch of the spirals disposed between the two rods 77 and 79. The total net initial tractive pitch of the spirals is defined as the total of the tractive pitch of each spiral as previously defined between the member receiving rods 77 and 79 less the width of all intervening intermediate rods 75. This latter factor is necessary since in such a situation the total tractive pitch of successive spirals is distorted by the fact that they overlap to the extent of the width of the rod.

It is addition-ally within the scope of this invention, as shown in FIGURE 3, to have the height 76 of the members equal to or greater than the height 78 of the spirals so as to prevent the spirals from being crushed and completely flattened and distorted under heavy loads. In this construction the plates absorb the crushing force of heavy loads acting substantially perpendicular to the sling surface.

In using slings 10 to lower extended lengths of pipeline 80 into a ditch by tractor means 91, as illustrated in FIGURE 6, the slings are loaded on the edge 92 towards which the pipe is sloping downwardly. This particular use results in off-center loading such that the load on one side 92 of the sling is at or above a predetermined load, such as one that stretches the belt member to a degree approaching its yield point while the load on the other side 94 is less than this predetermined l-oad.

FIGURE 7 shows the sling when subjected to such off-center loading. Not only does the supplemental load carry means prevent the spirals, assuming that the belt member is comprised of spirals, from being crushed and from stretching, for instance, above a degree approaching their yield point, but also it prevents the edge 92 of the sling bearing the greatest load from rupturing.

More particularly, the convolutions 30 adjacent to the side 92 hearing the greatest load are shown as being stretched to their yield point or any other predetermined point, thus the tractive pitch 64 of these convolutions are equal to the tractive pitch 62 of the plate members 52 adjacent to these convolutions. As such the load is di- Vided between the spirals and the plate members adjacent to the extended spirals. Contrary to the force distribution of straight line loading, the off-center loading results in an uneven distribution of force across the width of the sling. Therefore, the convolutions on the opposite side 94 of the sling have not been stretched to a degree approaching their yield point or any other predetermined point. Accordingly, the plate members adjacent to these convolutions are shown not seating on the rods and do not bear any of the load.

It will be appreciated that other types of loading may result in different distributions of force. However, in all situations the broad principle set forth in this invention is applicable, namely, that the supplemental load carrying means will assume the load jointly with the belt member as soon as the adjacent section of the belt member is stretched to or above certain point, such as a degree approaching its yield point, by a predetermined load.

It is also within the scope of this invention to cover the supple-mental load carrying members and belt member with an elastic coating means 96, as shown in FIG- URE 1, such that the coating will not interfere with the operation of the sling, but so that the surface of the sling adjacent to the load will not damage the load. For instance, in lowering pipe in the ground, it is desirable not to damage the covering surrounding the pipe.

While a preferred form of the invention has been illustrated in the drawings and discussed above, it should be adequately clear that considerable modification may be made thereto without departing from the principles of the invention. Therefore, the foregoing should be considered in an illustrative sense rather than a limiting sense, and accordingly the extent of this invention should be limited only by the spirit and scope of the claims appended hereto.

What is claimed is:

1. A metallic fabric sling comprising:

a pair of opposed support members;

a flexible belt member for carrying a normal load transversely secured at its ends to said support members, said belt members having a plurality of rods equally spaced from each other and positioned transversely of said belt member and secured thereto, said flexible belt member having a tractive pitch; and

supplemental load carrying means operatively associated with at least two of said rods and extending longitudinally along the longitudinal sides of said belt member, said supplemental load carrying means having a tractive pitch greater than the initial nonstretched tractive pitch of said flexible belt member and equal to the tractive pitch of said flexible belt member when subjected to and stretched by a predetermined tractive load so that under tractive loads up to said predetermined tractive load the only tractive load bearing element is said flexible belt member and at or above said predetermined tractive load, when said tractive pitch of said flexible belt member equals said tractive pitch of said supplemental load carrying means, said load is divided between said flexible belt member and said supplemental load carrying means.

2. The metallic sling as defined in claim 1 wherein said supplemental load carrying means is connected with at least two of said rods, said two rods having spaced therebetween, and extending parallel thereto, at least one other rod which is free of direct connection to said load carrying means.

3. The metallic fabric sling defined in claim 1 wherein said predetermined tractive load comprises a tractive load which will stretch the belt member to a degree approaching its yield point.

4. The metallic sling as defined in claim 1 wherein said supplemental load carrying means is pivotally connected to adjacent rods.

5. The metallic sling as defined in claim 1 wherein said supplemental load carrying means comprises a plurality of members, each of said members having opposed ends, said opposed ends being pivotally positioned on said rods and at least one of said opposed ends being slotted so as to be slidably positioned on said rod.

6. The metallic sling as defined in claim 1 additionally comprising an elastic coating covering at least the surfaces of said flexible metallic belt member and of said supplemental load carrying means which bear against said load so as to prevent said load from being damaged.

7. A metallic sling comprising:

a pair of opposed support members;

a belt for carrying the normal load of the sling secured at its end to the support members, said belt comprising a plurality of transversely disposed elongated helical spirals having arcuate vertexes at the ends of the convolutions thereof with adjacent spirals intermeshed and transversely extending rods interconnecting and extending through the alternate arcuate vertexes of the convolutions of adiacent spirals, the distance between said oppositely disposed rod-bearing arcuate vertexes of the convolutions defining the tractive pitch of said spirals; and

supplemental load carrying means pivotally connected to the ends of at least two of said rods and extending longitudinally along the sides of said belt, said supplemental load carrying means having a tractive pitch greater than the initial non-stretched tractive pitch of said spirals and equal to the tractive pitch of said spirals when subjected to a predetermined tractive load and stretched so that under tractive loads up to said predetermined tractive load the only tractive load bearing element is said spirals and at or above said predetermined tractive load, when said tractive pitch of said spirals equals said tractive pitch of said supplemental load carrying means, said load is divided between said spirals and said supplemental load carrying means.

8. The metallic sling as defined in claim 7 wherein said supplemental load carrying means is pivotally connected to the ends of two of said rods, said two rods being spaced from one another by at least one rod which is free of direct connection to said supplemental load carrying means.

9. The metallic sling as defined in claim 7 wherein said supplemental load carrying means is pivotally connected to the ends of adjacent rods.

10. The metallic sling as defined in claim 7 wherein said plurality of transversely disposed elongated helical spirals comprise spirals of right-hand twist and spirals of left-hand twist alternately disposed between said support members.

11. The metallic sling as defined in claim 7 additionally comprising means to attach said supplemental load carrying means to said support member.

12. The metallic sling as defined in claim 7 wherein said supplemental load carrying means is interconnected so as to extend continuously between said opposed support members along the opposed ends of said plurality of spirals.

13. The metallic sling as defined in claim 7 wherein said supplemental load carrying means comprises a plurality of substantially rigid members, each having opposed ends, said opposed ends being pivotally positioned on said ends of two of said rods and at least one of said opposed ends of said member being slotted so as to be slidably positioned on one of said two rods.

14. The metallic sling as defined in claim 13 wherein said members, being slidably and pivotally positioned on said ends of adjacent rods, have a tractive pitch greater than the initial tractive pitch of said spirals.

15. The metallic sling as defined in claim 13 wherein each of said members is slidably and pivotally positioned on one end of two of said rods and said two rods having spaced therebetween, and extending parallel thereto, at least one other rod which is free of direct connection to said members, each of said rods being spaced from adjacent rods by a distance substantially equal to the length of the convolution of the spiral receiving said adjacent rods, said length also defining the tractive pitch of said spiral, and wherein each of said members has a tractive pitch greater than the initial total net tractive pitch of said spirals extending between said two rods having said member positioned thereon.

16. The metallic fabric sling defined in claim 7, wherein said predetermined tractive load comprises a tractive load which will stretch the spirals to a degree approaching their yield point.

17. The metallic sling as defined in claim 15 wherein said initial tractive pitch of each of said members is equal to said total net tractive pitch of said spirals extending between said two rods having said member positioned thereon when said spirals are subjected to said predetermined tractive load so that under tractive loads up to said predetermined tractive load the only load bearing elements are said spirals and at or above said predetermined tractive load, when said total net tractive pitch of said spirals between said two rods equals said tractive pitch of said member, said load is divided between said member and said spirals.

18. The metallic sling as defined in claim 13 wherein the rods positioned between the opposed outermost rods have at least two members positioned thereon in an overlapping relation and alternately extending in opposite directions.

19. The metallic sling as defined in claim 18 wherein the number of members positioned on adjacent rods varies with respect to the tractive force exerted between said adjacent rods.

20. The metallic sling as defined in claim 13 wherein said members have a height at least equal to the height of said spirals when stretched .by said predetermined tractive load so as to prevent said spirals from being crushed under said load.

21. A metallic fabric sling comprising:

a pair of opposed support members;

a plurality of transversely disposed elongated helical spirals for carrying the normal load of the sling, said spirals being of right-hand twist and of left-hand twist alternatively disposed between said support members, said spirals having arcuatevertexes at the ends of the convolutions thereof intermeshed, and the oppositely disposed outermost spirals being operatively secured to said support members;

transversely extending rods interconnecting and extending through the alternate vertexes of the convolutions of adjacent spirals, the opposed outermost rods being transversely secured to said support members; and

a plurality of plate members, each having opposed ends with rod-receiving holes extending therethrough with at least one of said rod-receiving holes being slotted so as to be slidably positioned on said rod, said plate members being pivotally and slidably connected to the ends of adjacent rods along the opposed ends of said plurality of spirals, each of the rods positioned between the opposed outermost rods having at least two plate members positioned thereon in an overlapping relation and alternately extending in opposite directions so that said plate members are interconnected by means of said rods and extend continuously between said opposed support members, said plate members being operatively secured to said support members, and said plate members having an initial tractive pitch equal to said tractive pitch of said spirals when said spirals are subjected to loads to a degree approaching their yield point so that under loads to a degree approaching their yield point the only load bearing members are said spirals and at or above said degree, when said tractive pitch of said spirals equals said tractive pitch of said members, said load is divided between said members and said spirals.

22. A metallic sling as defined in claim 21 wherein said plate members have a height at least equal to the height of said spirals when stretched to a degree approaching their yield point so as to prevent said spirals from being crushed under said load.

23. A wire fabric comprising:

a plurality of transversely disposed elongated helical spirals having arcuate vertexes at the ends of the convolutions thereof with adjacent spirals intermeshed, the spirals having an initial tractive pitch;

a plurality of transversely extending rods interconnecting and extending through the alternate arcuate vertexes of the convolutions of adjacent spirals; and

a plurality of plate members, each having opposed ends with rod-receiving holes extending therethrough with at least one of said rod-receiving holes being slotted, said plate members being positioned on the ends of adjacent rods along the transverse ends of said plurality of spirals, said plate members having an initial tractive pitch equal to said tractive pitch of said spirals when said spirals are subjected to a predetermined tractive load so that under loads up to said predetermined tractive load the only load bearing elements are said spirals and at or above said predetermined tractive load, when said tractive pitch of said spirals equals said tractive pitch of said members, said load is divided between said members and said spirals.

24. The wire fabric defined in claim 23 wherein said predetermined tractive load comprises a tractive load which Will stretch the spirals to a degree approaching their yield point.

References Cited by the Examiner UNITED STATES PATENTS 3,167,344 1/1965 Applegarth 29474 FOREIGN PATENTS 666,404 7/ 1963 Canada.

GERALD M. FORLENZA, Primary Examiner.

G. F. ABRAHAM, Assistant Examiner. 

1. A METALLIC FABRIC SLING COMPRISING: A PAIR OF OPPOSED SUPPORT MEMBERS; A FLEXIBLE BELT MEMBER FOR CARRYING A NORMAL LOAD TRANSVERSELY SECURED AT ITS ENDS TO SAID SUPPORT MEMBERS, SAID BELT MEMBERS HAVING A PLURALITY OF RODS EQUALLY SPACED FROM EACH OTHER AND POSITIONED TRANSVERSELY OF SAID BELT MEMBER AND SECURED THERETO, SAID FLEXIBLE BELT MEMBER HAVING A TRACTIVE PITCH; AND SUPPLEMENTAL LOAD CARRYING MEANS OPERATIVELY ASSOCIATED WITH AT LEAST TWO OF SAID RODS AND EXTENDING LONGITUDINALLY ALONG THE LONGITUDINAL SIDES OF SAID BELT MEMBER, SAID SUPPLEMENTL LOAD CARRYING MEANS HAVING A TRACTIVE PITCH GREATER THAN THE INITIAL NONSTRETCHED TRACTIVE PITCH OF SAID FLEXIBLE BELT MEMBER AND EQUAL TO THE TRACTIVE PITCH OF SAID FLEXIBLE BELT 